Bare electronic chips typically need to be packaged in a package that provides thermal cooling and an electric circuit between each electrical connection of the chip and an external connector such as a pin or a ball.
The back side of a chip provides a convenient surface for removing heat generated by the circuits on the chip. Typically, a heat sink is pressed against the chip back side, sometimes using a heatsink compound to reduce thermal resistance. The circuit side of the chip typically provides pads that are connected to the chip's packaging using, for example, solder-ball connections.
Typical packaging includes a ball-grid array package having relatively large balls (e.g., in a ball-grid array) with relatively large spacings on one side of the package for external connections, and small closely spaced pads on the same side or the opposite side for connections to a ball-grid-array set of connections to the electronic chip (such as a processor or memory chip).
Such a package typically has a non-conductive substrate (such as a plastic film or layer) with conductive traces (wires) on or in a surface of the substrate. Some packages include multiple chips, such as one or more logic or processor chips, and/or one or more memory chips, such as a FLASH-type reprogrammable non-volatile memory. Optionally, a cover or encapsulant is used to enclose the chip or chips. Such packaging typically has poor thermal conductivity. Further, the various different coefficients of thermal expansion (CTEs) cause stress on the connections between ports of the packaging.
Chips that run at extremely high frequencies, e.g., upwards of 40 gigahertz, also have constraints as to the type, thickness, spacing, and layout of traces required to provide adequate signal capability. Further, such chips typically need to be run at very low voltages (e.g., about one volt) and very high currents (e.g., one hundred amps), which must be provided in order to achieve the desired high frequencies.
What is needed is a simple, inexpensive, reliable method and apparatus to fabricate packaging for electronic chips, so that the package provides high heat conductivity and dissipation, and high frequency response.